Latest research shows that oceans could be far less healthy without sharks

There are greater than 500 species of sharks on the planet’s oceans, from the 7-inch Dwarf Lanternshark To Whale sharks which may grow to over 10 metres in length. They are found from the polar waters to the equator, on the water surface and at depths of kilometres, within the open ocean, on coasts and even in some coastal rivers.

Given this diversity, it's not surprising that sharks serve many ecological functions. For example, the biggest specimens of some large predator species, resembling tiger and great white sharks, can play an outsized role in maintaining the balance between species. They do that by feeding on prey and sometimes just by being present and fearsome enough to cause prey species to vary their habits and locations.

In a newly published studyColleagues and I even have reviewed many years of research on the ecological role of sharks and examined their future in human-dominated oceans. We found that sharks play such diverse and sometimes essential roles in maintaining healthy oceans that their current decline is an urgent concern. Since 1970, global populations of sharks and rays have decreased by greater than 70%.

Humans are killing many shark species at unsustainable rates, primarily through overfishing. We see a necessity for nations to rethink where and the way they will protect sharks to make sure ocean health.

How sharks look after seagrass

More than 20 years of research along the distant coast of Western Australia shows that the presence of tiger sharks alone affects the whole seagrass ecosystem by changing where and the way large grazers resembling sea turtles and dugongs feed.

Tiger sharks nearby protects large areas of seagrass protected against overgrazing, allowing dense underwater meadows to develop that provide habitat for juvenile fish and shellfish. These species are essential food for other animals and for humans.

In places where tiger sharks have declined and turtle populations have increased, seagrasses are overgrazed. In Bermuda, for instance, the exploding turtle population has led to a almost complete collapse of seagrasses.

Great white sharks produce among the same effects. On the coast of California, where The variety of great white sharks is increasingOtters spend more time in the protection of protected inland waters and fewer time within the open waters of Monterey Bay. The otters hunt crabs, which in turn feed on grazing invertebrates resembling sea snails, which remove algae from sea grasses. More otters mean fewer crabs, more grazers and healthier seagrasses.

Kelp forests and reefs

Kelp forests are dense stands of enormous brown algae that grow in shallow areas near the coast. On the US West Coast, overhunting led to the extinction of local sea otter populations Beginning of the twentieth centuryThis led to enormous losses of kelp forests, as sea urchins – a favorite food of otters – Spreading and consuming kelp.

Over the last 50 years, otter populations recovered with federal protectionBut as white sharks expand their reach to the north, they’re Preventing the spread of otters because there aren’t any kelp forests during which the otters could hide.

Otters are unlikely to expand their range until kelp forests are established, complicating restoration efforts because otters don’t remove enough sea urchins for kelp to determine.

When sharks occur near coral reefs, Fish avoid sharks by staying near the protected reef. This reduces the grazing of seagrasses and algae over large areasHowever, there continues to be much to find out about when, where and the way sharks may be essential to coral reef health.

Food and nutrient sources

Sharks will also be prey. Some, including large species resembling great white sharksare essential sources of food for some killer whale populations all over the worldSmaller sharks, including blacktip sharks, can essential menu items for larger sharks, resembling great hammerhead sharks.

Because sharks eat their prey in a single place and excrete their waste in one other, they transport nutrients throughout the ocean. In the Pacific, for instance, grey reef sharks Moving nitrogen from the offshore waters where they feed, to the coral reefs where they spend their days and supply essential fertilizer for the ocean food webs.

In Florida's coastal watersJuvenile bull sharks feed during short visits to the ocean after which return to safer rivers with near-fresh water, where they spend most of their time and release nutrients through their excretions.

Sometimes the presence of sharks also helps other fish. In the open sea, sharks' rough scales are ideal scratching posts for fish to eliminate parasites.

Protecting the role of sharks

Our research shows that sharks play a various role in maintaining healthy oceans. We see essential implications for shark conservation.

The first step is to set goals that transcend simply ensuring the existence of sharks within the oceans, but as an alternative goal species that play a key ecological role.

Within populations, it will be significant to guard certain species of individual sharks. For example, the biggest tiger sharks shape the behavior of turtles and manatees, which advantages the ecosystems of seagrass stocks. Intensive fishing worldwide makes it difficult for giant sharks, which may reach as much as Decades and even centuries to survive and reach an ecologically essential size.

Working with local communities in coastal areas could construct support for safeguarding these large marine predators, much like how conservationists on land are working to Protecting legendary predators resembling wolvesStates could establish networks of enormous protected areas where shark fishing is prohibited, specializing in key areas where individual sharks could also be present.

Studies show that Sharks profit by creating protected areas, limiting shark fishing outside these zones and restricting the usage of fishing gear that harms sharks probably the most, like gill nets and longlinesWith a clearer understanding of the ecological value of sharks, my colleagues and I hope that targeted motion can be taken in any respect levels to guard these vital animals.